Antifouling and smart covalent organic framework composite nanofiltration membranes with light-gated molecular transport

Covalent organic framework (COF) holds great promise in affording precise and fast molecular separation. Inspired by the light-gated channels in cell membranes, we developed artificial light-gated molecular channel composite membranes by vacuum filtration COF with azobenzene (AZO) functional groups. The simple stimuli response could remotely adjust the membranes separation performance. The cis membranes with off state under ultraviolet (UV) light have higher dye rejection than trans membranes with on-state channels. The permeance of composite membranes increased from 19.56 to ∼ 42.30 L h−1 m−2 bar−1, dye (Rose Bengal (RB)) rejection increased from 94.40 % to 99.12 % after 10 min of 365 nm UV irradiation. In addition, the composite nanofiltration membranes exhibited good antifouling performance due to hydrophilic and highly smooth surface. By controlling the trans-to-cis AZO isomerization via UV /visible (Vis) light, the solvent permeance and dye rejection can be dynamically tuned due to the adjustable pore size.